c-- erase

Neutralize concept c: prompts that ask for it match the empty prompt. Default guidance does not write the opposite concept.

Category: velocity · Identity: erase

Syntax

c--
c--:0.5
c--:guidance=0
c--:guidance=1

c is required. A bare -- raises DSLError.

Velocity target

ESD, in a templated context c' (the GPU trainer samples ERASE_TEMPLATES; the 2-D fixture and loss_game pin that list to "{}" so the story is the axis, not the template):

v0 = v_f("")          # in context c'
vc = v_f(c')
v_t(c') → v0 − g (vc − v0)
loss = MSE

g is options["guidance"] if set, otherwise OpDefaults.erase_guidance.

Defaults

Knob	Value	Meaning
alpha	1	scales the MSE
guidance	0	neutralize: target is v0
guidance=1	phrase override	classic ESD overshoot, −CFG(c)

describe_phrase("red--") says "Neutralize". describe_phrase("red--:guidance=1") says ESD overshoot. There is no c!! or c/ synonym.

GEM and EA are not this glyph. They are ops_erase.erase_loss, selected by analysis_2d via erase_mode, not by the phrase. loss_game always uses rule_loss for --.

Composition

Keep+erase is already |:

red--|stripe#stripe
red--|#|stripe#stripe

# on the empty prompt is a no-op on this fixture (e("") = 0). The keep pin is the rule that names the concept you want held. See freeze and ../examples/keep_erase.md.

2-D verdict

../../dsl.md: right. Bare red-- lands on the origin. It does not write blue. red--:guidance=1 matches red=blue on this antipodal field, because −CFG(red) = CFG(blue). That identity is the fixture, not a reason to add an operator.

Failure modes

• Treating default -- as "write the antipode" is the old g=1 reading. The live default is g=0.
• A freeze whose prompt shares tokens with c can suppress the erase on a real encoder. Pick a token-disjoint keep.
• ; is not an erase and is not implemented (reward).

Example

from conceptmod.dsl import parse_phrase
bare = parse_phrase("red--")[0]
over = parse_phrase("red--:guidance=1")[0]
assert bare.options == {}
assert over.options["guidance"] == 1.0